Here is the full list of all 25 Seduce Me the Otome achievements. It takes around 1-2 hours to unlock all of the achievements on Windows.
Get Proposed to by Andrew.
Get Proposed to by James.
Kiss Erik under the Moonlight.
Share some Cake with Matthew.
Obtain True Freedom.
Be Baptized by Angels.
Give Damien his Humanity.
Start your Adventure with Diana.
Obtain True Power.
Find Harold Anderson's Magic Books.
Turn down sex, but keep your true love.
Accept Sam for the Man he is.
Preview the start of Seduce Me 2: The Demon War!
Witness Simon's Transformation with Diana and someone special...
Get Shot in the head by Malix.
Go To Paris with Naomi.
Prove Your Love to Suzu.
Be Eaten Alive by Diana's Pit Beast.
Unlock the Second Set of Bloopers!
Fight Malix Yourself.
Unlock the First Set of Bloopers!
Dodge Malix in time.
Impress the House Party Guests.
Prologue Completed!
Rename the Main Character.